Safety power disconnection for power distribution over power conductors to power consuming devices

ABSTRACT

Safety power disconnection for remote power distribution in power distribution systems is disclosed. The power distribution system includes one or more power distribution circuits each configured to remotely distribute power from a power source over current carrying power conductors to remote units to provide power for remote unit operations. A remote unit is configured to decouple power from the power conductors thereby disconnecting the load of the remote unit from the power distribution system. A current measurement circuit in the power distribution system measures current flowing on the power conductors and provides a current measurement to the controller circuit. The controller circuit is configured to disconnect the power source from the power conductors for safety reasons in response to detecting a current from the power source in excess of a threshold current level indicating a load.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.16/203,508, filed Nov. 28, 2018, which is a continuation ofInternational Application No. PCT/IL2018/050368, filed Mar. 29, 2018,which claims priority to U.S. Provisional Patent Application No.62/479,656, filed Mar. 31, 2017, all of which are incorporated herein byreference in their entireties.

BACKGROUND

The disclosure relates generally to distribution of power to one or morepower consuming devices over power wiring, and more particularly toremote distribution of power to remote units in a power distributionsystem, which may include distributed communications systems (DCS) suchas distributed antenna systems (DAS) for example, for operation of powerconsuming components of the remote units.

Wireless customers are increasingly demanding wireless communicationsservices, such as cellular communications services and Wi-Fi services.Thus, small cells, and more recently Wi-Fi services, are being deployedindoors. At the same time, some wireless customers use their wirelesscommunication devices in areas that are poorly serviced by conventionalcellular networks, such as inside certain buildings or areas where thereis little cellular coverage. One response to the intersection of thesetwo concerns has been the use of distributed antenna systems (DASs).DASs include remote antenna units (RAUs) configured to receive andtransmit communications signals to client devices within the antennarange of the RAUs. DASs can be particularly useful when deployed insidebuildings or other indoor environments where the wireless communicationdevices may not otherwise be able to effectively receive radio frequency(RF) signals from a source.

In this regard, FIG. 1 illustrates a wireless distributed communicationssystem (WDCS) 100 that is configured to distribute communicationsservices to remote coverage areas 102(1)-102(N), where ‘N’ is the numberof remote coverage areas. The WDCS 100 in FIG. 1 is provided in the formof a DAS 104. The DAS 104 can be configured to support a variety ofcommunications services that can include cellular communicationsservices, wireless communications services, such as RF identification(RFID) tracking, Wireless Fidelity (Wi-Fi), local area network (LAN),and wireless LAN (WLAN), wireless solutions (Bluetooth, Wi-Fi GlobalPositioning System (GPS) signal-based, and others) for location-basedservices, and combinations thereof, as examples. The remote coverageareas 102(1)-102(N) are created by and centered on RAUs 106(1)-106(N)connected to a central unit 108 (e.g., a head-end controller, a centralunit, or a head-end unit). The central unit 108 may be communicativelycoupled to a source transceiver 110, such as for example, a basetransceiver station (BTS) or a baseband unit (BBU). In this regard, thecentral unit 108 receives downlink communications signals 112D from thesource transceiver 110 to be distributed to the RAUs 106(1)-106(N). Thedownlink communications signals 112D can include data communicationssignals and/or communication signaling signals, as examples. The centralunit 108 is configured with filtering circuits and/or other signalprocessing circuits that are configured to support a specific number ofcommunications services in a particular frequency bandwidth (i.e.,frequency communications bands). The downlink communications signals112D are communicated by the central unit 108 over a communications link114 over their frequency to the RAUs 106(1)-106(N).

With continuing reference to FIG. 1, the RAUs 106(1)-106(N) areconfigured to receive the downlink communications signals 112D from thecentral unit 108 over the communications link 114. The downlinkcommunications signals 112D are configured to be distributed to therespective remote coverage areas 102(1)-102(N) of the RAUs106(1)-106(N). The RAUs 106(1)-106(N) are also configured with filtersand other signal processing circuits that are configured to support allor a subset of the specific communications services (i.e., frequencycommunications bands) supported by the central unit 108. In anon-limiting example, the communications link 114 may be a wiredcommunications link, a wireless communications link, or an opticalfiber-based communications link. Each of the RAUs 106(1)-106(N) mayinclude an RF transmitter/receiver 116(1)-116(N) and a respectiveantenna 118(1)-118(N) operably connected to the RF transmitter/receiver116(1)-116(N) to wirelessly distribute the communications services touser equipment (UE) 120 within the respective remote coverage areas102(1)-102(N). The RAUs 106(1)-106(N) are also configured to receiveuplink communications signals 112U from the UE 120 in the respectiveremote coverage areas 102(1)-102(N) to be distributed to the sourcetransceiver 110.

Because the RAUs 106(1)-106(N) include components that require power tooperate, such as the RF transmitter/receivers 116(1)-116(N) for example,it is necessary to provide power to the RAUs 106(1)-106(N). In oneexample, each RAU 106(1)-106(N) may receive power from a local powersource. In another example, the RAUs 106(1)-106(N) may be poweredremotely from a remote power source(s). For example, the central unit108 may include a power source 122 that is configured to remotely supplypower over the communications links 114 to the RAUs 106(1)-106(N). Forexample, the communications links 114 may be cable that includeselectrical conductors for carrying current (e.g., direct current (DC))to the RAUs 106(1)-106(N). If the WDCS 100 is an optical fiber-basedWDCS in which the communications links 114 include optical fibers, thecommunications links 114 may by a “hybrid” cable that includes opticalfibers for carrying the downlink and uplink communications signals 112D,112U and separate electrical conductors for carrying current to the RAUs106(1)-106(N).

Some regulations, such as IEC 60950-21, may limit the amount of directcurrent (DC) that is remote delivered by the power source 122 over thecommunications links 114 to less than the amount needed to power theRAUs 106(1)-106(N) during peak power consumption periods for safetyreasons, such as in the event a human contacts the wire. One solution toremote power distribution limitations is to employ multiple conductorsand split current from the power source 122 over the multipleconductors, such that the current on any one electrical conductor isbelow the regulated limit. Another solution includes delivering remotepower at a higher voltage so that a lower current can be distributed atthe same power level. For example, assume that 300 Watts of power is tobe supplied to a RAU 106(1)-106(N) by the power source 122 through acommunications link 114. If the voltage of the power source 122 is 60Volts (V), the current will be 5 Amperes (A) (i.e., 300 W/60 V).However, if a 400 Volt power source 122 is used, then the currentflowing through the wires will be 0.75 A. However, delivering highvoltage through electrical conductors may be further regulated toprevent an undesired current from flowing through a human in the eventthat a human contacts the electrical conductor. Thus, these safetymeasures may require other protections, such as the use of protectionconduits, which may make installations more difficult and add cost.

No admission is made that any reference cited herein constitutes priorart. Applicant expressly reserves the right to challenge the accuracyand pertinency of any cited documents.

SUMMARY

Embodiments of the disclosure relate to safety power disconnection forpower distribution over power conductors to power consuming devicessystems. As a non-limiting example, a such power distribution may beprovided in a distributed communications systems (DCS). For example, theDCS may be a wireless DCS, such as a distributed antenna system (DAS)that is configured to distribute communications signals, includingwireless communications signals, from a central unit to a plurality ofremote units over physical communications media, to then be distributedfrom the remote units wirelessly to client devices in wirelesscommunication range of a remote unit. In exemplary aspects disclosedherein, the DCS includes one or more power distribution systems eachconfigured to remotely distribute power from a power source over currentcarrying electrical conductors (“power conductors”) to remote units toprovide power-to-power consuming components of the remote units foroperation. For example, a power distribution system may be installed oneach floor of a multi-floor building in which the DCS is installed toprovide power to the remote units installed on a given floor. Each powerdistribution system includes a current measurement circuit configured tomeasure current delivered by the power source over the power conductorsto remote units. Each power distribution system also includes acontroller circuit configured to communicate over a managementcommunications link to the remote units receiving power from the powerdistribution circuit. The remote unit is configured to be decoupled fromthe power conductors from its power consuming components therebydisconnecting the load of the remote unit from the power distributionsystem. The current measurement circuit then measures current flowing onthe power conductors and provides a current measurement to thecontroller circuit. The controller circuit is configured to disconnectthe power source from the power conductors for safety reasons inresponse to detection of a load based on detecting a current from thepower source in excess of a threshold current level. For example, aperson contacting the power conductors will present a load to the powersource that will cause a current to flow from the power source over thepower conductors. If another load is not contacting the powerconductors, no current (or only a small amount current due to currentleakages for example) should flow from the power source over the powerconductors. The controller circuit can be configured to wait a period oftime and/or until a manual reset instruction is received, beforeconnecting the power source from the power conductors and remote unitcoupling its power consuming components to the power conductors to onceagain allow current to flow from the power source to the remote unitsserviced by the power distribution system.

In this regard, in one exemplary aspect, a power distribution system isdisclosed. The power distribution system comprises one or more powerdistribution circuits. The one or more power distribution circuits eachcomprise a distribution power input configured to receive currentdistributed by a power source. The one or more power distributioncircuits each also comprise a distribution power output configured todistribute the received current over a power conductor coupled to anassigned remote unit among a plurality of remote units. The one or morepower distribution circuits each also comprise a distribution switchcircuit coupled between the distribution power input and thedistribution power output. The distribution switch circuit comprises adistribution switch control input configured to receive a distributionpower connection control signal indicating a distribution powerconnection mode. The distribution switch circuit is configured to beclosed to couple the distribution power input to the distribution poweroutput in response to the distribution power connection mode indicatinga distribution power connect state. The distribution switch circuit isfurther configured to be opened to decouple the distribution power inputfrom the distribution power output in response to the distribution powerconnection mode indicating a distribution power disconnect state. Theone or more power distribution circuits each also comprise a currentmeasurement circuit coupled to the distribution power output andcomprising a current measurement output. The current measurement circuitis configured to measure a current at the distribution power output andgenerate a current measurement on the current measurement output basedon the measured current at the distribution power output. The powerdistribution system also comprises a controller circuit. The controllercircuit comprises one or more current measurement inputs communicativelycoupled to the one or more current measurement outputs of the one ormore current measurement circuits of the one or more power distributioncircuits. The controller circuit is configured to, for a powerdistribution circuit among the one or more power distribution circuits,generate the distribution power connection control signal indicating thedistribution power connection mode to the distribution switch controlinput of the power distribution circuit indicating the distributionpower connect state, determine if the measured current on a currentmeasurement input among the one or more current measurement inputs ofthe power distribution circuit exceeds a predefined threshold currentlevel when the distribution switch circuit is closed to couple thedistribution power input to the distribution power output; and inresponse to the measured current of the power distribution circuitexceeding the predefined threshold current level, communicate thedistribution power connection control signal indicating the distributionpower connection mode to the distribution switch control input of thepower distribution circuit indicating the distribution power disconnectstate.

An additional aspect of the disclosure relates to a method ofdisconnecting current from a power source. The method comprisesdecoupling current from a power conductor to a remote unit. The methodfurther comprises measuring a current received from a power sourcecoupled to the power conductor. The method further comprises determiningif the measured current exceeds a predefined threshold current level.The method further comprises, in response to the measured currentexceeding the predefined threshold current level, communicating adistribution power connection control signal comprising a distributionpower connection mode indicating a distribution power disconnect stateto cause the power conductor to be decoupled from the power source.

An additional aspect of the disclosure relates to a distributedcommunications system (DCS). The DCS comprises a central unit. Thecentral unit is configured to distribute received one or more downlinkcommunications signals over one or more downlink communications links toone or more remote units. The central unit is also configured todistribute received one or more uplink communications signals from theone or more remote units from one or more uplink communications links toone or more source communications outputs. The DCS also comprises aplurality of remote units. Each remote unit among the plurality ofremote units comprises a remote power input coupled to a power conductorcarrying current from a power distribution circuit. Each remote unitamong the plurality of remote units also comprises a remote switchcontrol circuit configured to generate a remote power connection signalindicating a remote power connection mode. Each remote unit among theplurality of remote units also comprises a remote switch circuitcomprising a remote switch input configured to receive the remote powerconnection signal. The remote switch circuit is configured to be closedto couple to the remote power input in response to the remote powerconnection mode indicating a remote power connect state. The remoteswitch circuit is further configured to be opened to decouple from theremote power input in response to the remote power connection modeindicating a remote power disconnect state. The remote unit isconfigured to distribute the received one or more downlinkcommunications signals received from the one or more downlinkcommunications links, to one or more client devices. The remote unit isalso configured to distribute the received one or more uplinkcommunications signals from the one or more client devices to the one ormore uplink communications links. The DCS also comprises a powerdistribution system. The power distribution system comprises one or morepower distribution circuits. Each power distribution circuit of the oneor more power distribution circuits comprises a distribution power inputconfigured to receive current distributed by a power source. Each powerdistribution circuit of the one or more power distribution circuits alsocomprises a distribution power output configured to distribute thereceived current over a power conductor coupled to an assigned remoteunit among a plurality of remote units. Each power distribution circuitof the one or more power distribution circuits also comprises adistribution switch circuit coupled between the distribution power inputand the distribution power output, the distribution switch circuitcomprising a distribution switch control input configured to receive adistribution power connection control signal indicating a distributionpower connection mode. The distribution switch circuit is configured tobe closed to couple the distribution power input to the distributionpower output in response to the distribution power connection modeindicating a distribution power connect state. The distribution switchcircuit is further configured to be opened to decouple the distributionpower input from the distribution power output in response to thedistribution power connection mode indicating a distribution powerdisconnect state. Each power distribution circuit of the one or morepower distribution circuits also comprises a current measurement circuitcoupled to the distribution power output and comprising a currentmeasurement output. The current measurement circuit configured tomeasure a current at the distribution power output and generate acurrent measurement on the current measurement output based on themeasured current at the distribution power output. The powerdistribution system also comprises a controller circuit. The controllercircuit comprises one or more current measurement inputs communicativelycoupled to the one or more current measurement outputs of the one ormore current measurement circuits of the one or more power distributioncircuits. The controller circuit is configured to, for a powerdistribution circuit among the one or more power distribution circuits:generate the distribution power connection control signal indicating thedistribution power connection mode to the distribution switch controlinput of the power distribution circuit indicating the distributionpower connect state; determine if the measured current on a currentmeasurement input among the one or more current measurement inputs ofthe power distribution circuit exceeds a predefined threshold currentlevel; and in response to the measured current of the power distributioncircuit exceeding the predefined threshold current level, communicatethe distribution power connection control signal comprising thedistribution power connection mode to the distribution switch controlinput of the power distribution circuit indicating the distributionpower disconnect state.

Additional features and advantages will be set forth in the detaileddescription which follows and, in part, will be readily apparent tothose skilled in the art from the description or recognized bypracticing the embodiments as described in the written description andclaims hereof, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary and are intendedto provide an overview or framework to understand the nature andcharacter of the claims.

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary wireless distributedcommunications system (DCS) in the form of a distributed antenna system(DAS);

FIG. 2 is a schematic diagram of an exemplary optical-fiber based DCS inthe form of a DAS configured to distribute communications signalsbetween a central unit and a plurality of remote units, and that caninclude one or more power distribution systems configured to distributepower to a plurality of remote units and provide a safety powerdisconnect of the power source to remote units;

FIG. 3A is a partially schematic cut-away diagram of an exemplarybuilding infrastructure in which a DCS in FIG. 2 can be provided;

FIG. 3B is a more detailed schematic diagram of the DCS in FIG. 3A;

FIG. 4 is a schematic diagram illustrating a power distribution systemthat can be included in the DCS in FIGS. 2-3B as an example, wherein thepower distribution system is configured to provide safety powerdisconnect of the power source to a remote unit in response to ameasured current from the connected power source when the remote unit isdecoupled from the power source during a testing phase;

FIG. 5 is a timing diagram illustrating an exemplary timing sequence ofthe controller circuit in the power distribution system in the DCS inFIG. 4;

FIG. 6 is a flowchart illustrating an exemplary process of thecontroller circuit in the power distribution system of the DCS in FIG. 4coupling the remote unit during a normal operation phase and instructingthe remote unit to decouple from the power source during testing phasesto then measure current from the power source during a testing phase;

FIG. 7 is a graph illustrating exemplary safe and unsafe regions of bodycurrent for a given current impulse time;

FIG. 8 is a schematic diagram illustrating the DCS in FIG. 4 with thepower distribution circuit configured to distribute power from a powersource to a plurality of remote units to provide power for operation ofthe remote units, and provide a safety power disconnect of the powersource to remote units in response to a measured current from the powersource;

FIG. 9 is a schematic diagram illustrating an exemplary powerdistribution system that can be employed as the power distributionsystems in the DCS in FIG. 8;

FIG. 10 is a schematic diagram illustrating additional exemplary detailof the controller circuit of the power distribution system in FIG. 8;

FIG. 11 is a diagram of another exemplary power distribution system thatcan be provided in the DCS in FIGS. 2 and 3, wherein the powerdistribution system is configured to provide safety power disconnect ofthe power source to a remote unit in response to a measured differentialcurrent from the connected power source when the remote unit isdecoupled from the power source during a testing phase; and

FIG. 12 is a schematic diagram of a generalized representation of anexemplary controller that can be included in any component in a DCS,including but not limited to the controller circuits in the powerdistribution systems for coupling a remote unit to a power source duringa normal operation phase and instructing the remote unit to decouplefrom the power source during testing phases to then measure current fromthe power source during a testing phase, wherein an exemplary computersystem is adapted to execute instructions from an exemplary computerreadable link.

DETAILED DESCRIPTION

Embodiments of the disclosure relate to safety power disconnection forpower distribution over power conductors to power consuming devicessystems. As a non-limiting example, a such power distribution may beprovided in a distributed communications systems (DCS). For example, theDCS may be a wireless DCS, such as a distributed antenna system (DAS)that is configured to distribute communications signals, includingwireless communications signals, from a central unit to a plurality ofremote units over physical communications media, to then be distributedfrom the remote units wirelessly to client devices in wirelesscommunication range of a remote unit. In exemplary aspects disclosedherein, the DCS includes one or more power distribution systems eachconfigured to remotely distribute power from a power source over currentcarrying electrical conductors (“power conductors”) to remote units toprovide power-to-power consuming components of the remote units foroperation. For example, a power distribution system may be installed oneach floor of a multi-floor building in which the DCS is installed toprovide power to the remote units installed on a given floor. Each powerdistribution system includes a current measurement circuit configured tomeasure current delivered by the power source over the power conductorsto remote units. Each power distribution system also includes acontroller circuit configured to communicate over a managementcommunications link to the remote units receiving power from the powerdistribution circuit. The remote unit is configured to be decoupled fromthe power conductors from its power consuming components therebydisconnecting the load of the remote unit from the power distributionsystem. The current measurement circuit then measures current flowing onthe power conductors and provides a current measurement to thecontroller circuit. The controller circuit is configured to disconnectthe power source from the power conductors for safety reasons inresponse to detection of a load based on detecting a current from thepower source in excess of a threshold current level. For example, aperson contacting the power conductors will present a load to the powersource that will cause a current to flow from the power source over thepower conductors. If another load is not contacting the powerconductors, no current (or only a small amount current due to currentleakages for example) should flow from the power source over the powerconductors. The controller circuit can be configured to wait a period oftime and/or until a manual reset instruction is received, beforeconnecting the power source from the power conductors and remote unitcoupling its power consuming components to the power conductors to onceagain allow current to flow from the power source to the remote unitsserviced by the power distribution system.

Before discussing exemplary details of power distribution systems,including power distribution systems that can be included in a DCS forremotely distributing power to remote units and provide safety powerdisconnect of a power source to the remote units starting at FIG. 4, anexemplary power distribution system that can include remote powerdistribution is described in FIGS. 2-3B.

In this regard, FIG. 2 is a schematic diagram of such an exemplary powerdistribution system 250. In this example, the power distribution system250 is provided in the form of a DCS 200, which is a distributed antennasystem (DAS) 202 in this example. Note that the power distributioncircuit 250 is not limited to a DCS or being provided in a DCS. A DAS isa system that is configured to distribute communications signals,including wireless communications signals, from a central unit to aplurality of remote units over physical communications media, to then bedistributed from the remote units wirelessly to client devices inwireless communication range of a remote unit. The DAS 202 in thisexample is an optical fiber-based DAS that is comprised of three (3)main components. One or more radio interface circuits provided in theform of radio interface modules (RIMS) 204(1)-204(T) are provided in acentral unit 206 to receive and process downlink electricalcommunications signals 208D(1)-208D(S) prior to optical conversion intodownlink optical communications signals. The downlink electricalcommunications signals 208D(1)-208D(S) may be received from a basetransceiver station (BTS) or baseband unit (BBU) as examples. Thedownlink electrical communications signals 208D(1)-208D(S) may be analogsignals or digital signals that can be sampled and processed as digitalinformation. The RIMs 204(1)-204(T) provide both downlink and uplinkinterfaces for signal processing. The notations “1-S” and “1-T” indicatethat any number of the referenced component, 1-S and 1-T, respectively,may be provided.

With continuing reference to FIG. 2, the central unit 206 is configuredto accept the plurality of RIMS 204(1)-204(T) as modular components thatcan easily be installed and removed or replaced in a chassis. In oneembodiment, the central unit 206 is configured to support up to twelve(12) RIMs 204(1)-204(12). Each RIM 204(1)-204(T) can be designed tosupport a particular type of radio source or range of radio sources(i.e., frequencies) to provide flexibility in configuring the centralunit 206 and the DAS 202 to support the desired radio sources. Forexample, one RIM 204 may be configured to support the PersonalCommunication Services (PCS) radio band. Another RIM 204 may beconfigured to support the 700 MHz radio band. In this example, byinclusion of these RIMS 204, the central unit 206 could be configured tosupport and distribute communications signals, including those for thecommunications services and communications bands described above asexamples.

The RIMs 204(1)-204(T) may be provided in the central unit 206 thatsupport any frequencies desired, including but not limited to licensedUS FCC and Industry Canada frequencies (824-849 MHz on uplink and869-894 MHz on downlink), US FCC and Industry Canada frequencies(1850-1915 MHz on uplink and 1930-1995 MHz on downlink), US FCC andIndustry Canada frequencies (1710-1755 MHz on uplink and 2110-2155 MHzon downlink), US FCC frequencies (698-716 MHz and 776-787 MHz on uplinkand 728-746 MHz on downlink), EU R & TTE frequencies (880-915 MHz onuplink and 925-960 MHz on downlink), EU R & TTE frequencies (1710-1785MHz on uplink and 1805-1880 MHz on downlink), EU R & TTE frequencies(1920-1980 MHz on uplink and 2110-2170 MHz on downlink), US FCCfrequencies (806-824 MHz on uplink and 851-869 MHz on downlink), US FCCfrequencies (896-901 MHz on uplink and 929-941 MHz on downlink), US FCCfrequencies (793-805 MHz on uplink and 763-775 MHz on downlink), and USFCC frequencies (2495-2690 MHz on uplink and downlink).

With continuing reference to FIG. 2, the received downlink electricalcommunications signals 208D(1)-208D(S) are provided to a plurality ofoptical interfaces provided in the form of optical interface modules(OIMs) 210(1)-210(W) in this embodiment to convert the downlinkelectrical communications signals 208D(1)-208D(S) (“downlink electricalcommunications signals 208D(1)-208D(S)”) into downlink opticalcommunications signals 212D(1)-212D(S). The notation “1-W” indicatesthat any number of the referenced component 1-W may be provided. TheOIMs 210 may include one or more optical interface components (OICs)that contain electrical-to-optical (E-O) converters 216(1)-216(W) toconvert the received downlink electrical communications signals208D(1)-208D(S) into the downlink optical communications signals212D(1)-212D(S). The OIMs 210 support the radio bands that can beprovided by the RIMS 204, including the examples previously describedabove. The downlink optical communications signals 212D(1)-212D(S) arecommunicated over a downlink optical fiber communications link 214D to aplurality of remote units 218(1)-218(X) provided in the form of remoteantenna units in this example. The notation “1-X” indicates that anynumber of the referenced component 1-X may be provided. One or more ofthe downlink optical communications signals 212D(1)-212D(S) can bedistributed to each remote unit 218(1)-218(X). Thus, the distribution ofthe downlink optical communications signals 212D(1)-212D(S) from thecentral unit 206 to the remote units 218(1)-218(X) is in apoint-to-multipoint configuration in this example.

With continuing reference to FIG. 2, the remote units 218(1)-218(X)include optical-to-electrical (O-E) converters 220(1)-220(X) configuredto convert the one or more received downlink optical communicationssignals 212D(1)-212D(S) back into the downlink electrical communicationssignals 208D(1)-208D(S) to be wirelessly radiated through antennas222(1)-222(X) in the remote units 218(1)-218(X) to user equipment (notshown) in the reception range of the antennas 222(1)-222(X). The OIMs210 may also include O-E converters 224(1)-224(W) to convert thereceived uplink optical communications signals 212U(1)-212U(X) from theremote units 218(1)-218(X) into the uplink electrical communicationssignals 226U(1)-226U(S) as will be described in more detail below.

With continuing reference to FIG. 2, the remote units 218(1)-218(X) arealso configured to receive uplink electrical communications signals228U(1)-228U(X) received by the respective antennas 222(1)-222(X) fromclient devices in wireless communication range of the remote units218(1)-218(X). The uplink electrical communications signals228U(1)-228U(S) may be analog signals or digital signals that can besampled and processed as digital information. The remote units218(1)-218(X) include E-O converters 229(1)-229(X) to convert thereceived uplink electrical communications signals 228U(1)-228U(X) intouplink optical communications signals 212U(1)-212U(X). The remote units218(1)-218(X) distribute the uplink optical communications signals212U(1)-212U(X) over an uplink optical fiber communication link 214U tothe OIMs 210(1)-210(W) in the central unit 206. The O-E converters224(1)-224(W) convert the received uplink optical communications signals212U(1)-212U(X) into uplink electrical communications signals230U(1)-230U(X), which are processed by the RIMs 204(1)-204(T) andprovided as the uplink electrical communications signals 230U(1)-230U(X)to a source transceiver such as a base transceiver station (BTS) orbaseband unit (BBU).

Note that the downlink optical fiber communications link 214D and theuplink optical fiber communications link 214U coupled between thecentral unit 206 and the remote units 218(1)-218(X) may be a commonoptical fiber communications link, wherein for example, wave divisionmultiplexing (WDM) may be employed to carry the downlink opticalcommunications signals 212D(1)-212D(S) and the uplink opticalcommunications signals 212U(1)-212U(X) on the same optical fibercommunications link. Alternatively, the downlink optical fibercommunications link 214D and the uplink optical fiber communicationslink 214U coupled between the central unit 206 and the remote units218(1)-218(X) may be single, separate optical fiber communications link,wherein for example, wave division multiplexing (WDM) may be employed tocarry the downlink optical communications signals 212D(1)-212D(S) on onecommon downlink optical fiber and the uplink optical communicationssignals 212U(1)-212U(X) carried on a separate, only uplink opticalfiber. Alternatively, the downlink optical fiber communications link214D and the uplink optical fiber communications link 214U coupledbetween the central unit 206 and the remote units 218(1)-218(X) may beseparate optical fibers dedicated to and providing a separatecommunications link between the central unit 206 and each remote unit218(1)-218(X).

The DCS 200 in FIG. 2 can be provided in an indoor environment asillustrated in FIG. 3A. FIG. 3A is a partially schematic cut-awaydiagram of a building infrastructure 232 employing the DCS 200. FIG. 3Bis a schematic diagram of the DCS 200 installed according to thebuilding infrastructure 232 in FIG. 3A.

With reference to FIG. 3A, the building infrastructure 232 in thisembodiment includes a first (ground) floor 234(1), a second floor234(2), and a Fth floor 234(F), where ‘F’ can represent any number offloors. The floors 234(1)-234(F) are serviced by the central unit 206 toprovide antenna coverage areas 236 in the building infrastructure 232.The central unit 206 is communicatively coupled to a signal source 238,such as a BTS or BBU, to receive the downlink electrical communicationssignals 208D(1)-208D(S). The central unit 206 is communicatively coupledto the remote units 218(1)-218(X) to receive optical uplinkcommunications signals 212U(1)-212U(X) from the remote units218(1)-218(X) as previously described in FIG. 2A. The downlink anduplink optical communications signals 212D(1)-212D(S), 212U(1)-212U(X)are distributed between the central unit 206 and the remote units218(1)-218(X) over a riser cable 240 in this example. The riser cable240 may be routed through interconnect units (ICUs) 242(1)-242(F)dedicated to each floor 234(1)-234(F) for routing the downlink anduplink optical communications signals 212D(1)-212D(S), 212U(1)-212U(X)to the remote units 218(1)-218(X). The ICUs 242(1)-242(F) may alsoinclude respective power distribution circuits 244(1)-244(F) thatinclude power sources as part of the power distribution system 250,wherein the power distribution circuits 244(1)-244(F) are configured todistribute power remotely to the remote units 218(1)-218(X) to providepower for operating the power consuming components in the remote units218(1)-218(X). For example, array cables 245(1)-245(F) may be providedand coupled between the ICUs 242(1)-242(F) that contain both opticalfibers to provide the respective downlink and uplink optical fibercommunications media 214D(1)-214D(F), 214U(1)-214U(F) and powerconductors 246(1)-246(F) (e.g., electrical wire) to carry current fromthe respective power distribution circuits 244(1)-244(F) to the remoteunits 218(1)-218(X).

With reference to the DCS 200 shown in FIG. 3B, the central unit 206 mayinclude a power supply circuit 252 to provide power to the RIMS204(1)-204(T), the OIMs 210(1)-210(W), and radio distribution circuits(RDCs) 254, 256. The downlink electrical communications signals208D(1)-208D(S) and the uplink electrical communications signals226U(1)-226U(S) are routed from between the RIMs 204(1)-204(T) and theOIMs 210(1)-210(W) through RDCs 254, 256. In one embodiment, the RDCs254, 256 can support sectorization in the DCS 200, meaning that onlycertain downlink electrical communications signals 208D(1)-208D(S) arerouted to certain RIMS 204(1)-204(T). A power supply circuit 258 mayalso be provided to provide power to the OIMs 210(1)-210(W). Aninterface 260, which may include web and network management system (NMS)interfaces, may also be provided to allow configuration andcommunication to the components of the central unit 206. Amicrocontroller, microprocessor, or other control circuitry, called ahead-end controller (HEC) 262 may be included in central unit 206 toprovide control operations for the central unit 206 and the DCS 200.

As discussed above in reference to FIG. 3A and with continuing referenceto FIG. 3B, the power distribution circuits 244(1)-244(F) may beprovided in the DCS 200 to remotely supply power to the remote units218(1)-218(X) for operation. For example, the power distributioncircuits 244(1)-244(F) may be configured to supply direct current (DC)power due to relative short distances and as a safer option thandistributing alternating current (AC) power. Further, distributing DCpower may avoid the need to provide AC-DC conversion circuitry in theremote units 218(1)-218(X) saving area and cost. Remotely distributingpower to the remote units 218(1)-218(X) may be desired if it isdifficult or not possible to locally provide power to the remote units218(1)-218(X) in their installed locations. For example, the remoteunits 218(1)-218(X) may be installed in ceilings or on walls of abuilding. Even if local power is available, the local power may not becapable of supplying enough power-to-power the number of remote units218(1)-218(X) desired. However, regulations may also limit the amount ofDC that is remotely delivered by the power distribution circuits244(1)-244(F) over the power conductors 246(1)-246(F) to less than theamount needed to power the remote units 218(1)-218(X) during peak powerconsumption periods for safety reasons, such as in the event a humancontacts the power conductors 246(1)-246(F). One solution to theseremote power distribution limitations is to employ multiple powerconductors 246(1)-246(F) and split current from the power distributioncircuits 244(1)-244(F) over the multiple power conductors 246(1)-246(F)as shown, such that the current on any one power conductor 246(1)-246(F)is below the regulated limit. Another solution includes deliveringremote power at a higher voltage so that a lower current can bedistributed at the same power level. For example, assume that 300 Wattsof power is to be supplied to a remote unit 218(1)-218(X) by a powerdistribution circuit 244(1)-244(F) through a respective power conductor246(1)-246(F). If the voltage of the power distribution circuit244(1)-244(F) is 60 Volts (V), the current will be 5 Amperes (A) (i.e.,300 W/60 V). However, if a 400 Volt is employed, then the currentflowing through the wires will be 0.75 A. However, delivering highvoltage through power conductors 246(1)-246(F) may be further regulatedto prevent an undesired current from flowing through a human in theevent that a human contacts the power conductor 246(1)-246(F). Thus,these safety measures may require other protections, such as the use ofprotection conduits for the array cables 245(1)-245(F), which may makeinstallations of the DSC 200 more difficult and add cost.

In this regard, FIG. 4 is a schematic diagram illustrating a powerdistribution circuit 244 of the power distribution system 250 in theform of the DCS 200 in FIGS. 2-3B. The power distribution circuit 244 inFIG. 4 can be any of the power distribution circuits 244(1)-244(F) inFIGS. 3A and 3B. The power distribution circuit 244 includes a powersource 400 that is configured to supply power (i.e., current I₁) to bedistributed over the power conductors 246+, 246− to a load 401 of theremote unit 218 to provide power to the remote unit 218 for operation ofits consuming components. For example, the power source 400 may be aDC/DC power supply (e.g., 48V DC/350V DC) or AC/DC power supply (e.g.,AC/350 V DC). The power source 400 may be included in the same housingor chassis as the power distribution circuit 244, or separate from thepower distribution circuit 244. As will be discussed in more detailbelow, the power distribution circuit 244 illustrated in FIG. 4 isconfigured to provide safety power disconnect of the power source 400from the power conductors 246+, 246− in response to a measured currentI₂ from the connected power source 400 when the remote unit 218 isdecoupled from the power source 400 during a testing phase. The powerdistribution circuit 244 includes a current measurement circuit 402configured to measure the current I₂ delivered by the power source 400to a distribution power output 403 coupled to the power conductors 246+,246− as an indication of a safety condition as to whether an externalload, such as a human, is in contact on the power conductors 246+, 246−.If another load is not contacting the power conductors 246+, 246−, thismeans no current or only a small amount of current, due to currentleakages for example, should flow from the power source 400 to the powerconductors 246+, 246−. However, if an external load 418, such as aperson, is contacting the power conductors 246+, 246−, this load 418will present a load to the power source 400 that will cause the currentI₂ to flow from the power source 400 over the power conductors 246+,246−. This current I₂ can be detected as a method of detecting anexternal load 418, such as a human, in contact with the power conductors246+, 246− to cause the power distribution circuit 244 to decouple thepower source 400 from the power conductors 246+, 246− as a safetymeasure.

In this regard, with reference to FIG. 4, the power distribution circuit244 includes a controller circuit 404. The controller circuit 404 isconfigured to send a distribution power connection control signal 406indicating a distribution power connection state to close a distributionswitch circuit 408 to couple the power source 400 to the currentmeasurement circuit 402. The closing of the distribution switch circuit408 allows current I₁ to be drawn from the power source 400 and becarried by the power conductor 246+ to a remote power input 409 of theremote unit 218. To determine if an external load 418 other than theremote circuit 218, such as a human, is contacting the power conductors246+, 246−, the controller circuit 404 could be configured tocommunicate over a management communications link 410 to the remote unit218. The management communications link 410 may be electrical conductors(e.g. copper wire) or optical fiber medium as examples. The managementcommunications link 410 may be a bidirectional communications linkconfigured to carry a full duplex signal at a carrier frequency, such as1.5 MHz for example. The controller circuit 404 is configured to send aremote power connection signal 412 indicating a remote power disconnectstate to a switch control circuit 414 coupled to the managementcommunications link 410. In response, the switch control circuit 414 isconfigured to send a remote power connection signal 411 indicating theremote power disconnect state to a remote switch input 413 to open aremote switch circuit 416 in the remote unit 218 to decouple the remoteunit 218 from power conductor 246+ thereby disconnecting the load of theremote unit 218 from the power distribution circuit 244. This allows ameasurement current on the power conductors 246+, 246− to be associatedwith an external load 418 and not the load of the remote unit 218. Whenthe remote switch circuit 416 is open, power is provided to the load 401from the capacitor C₁. The current measurement circuit 402 measures thecurrent on the power conductors 246+, 246− while the remote unit 218 isdecoupled from the power source 400. If an external load 418 is notcontacting the power conductors 246+, 246−, this means no current (oronly a small amount of current due to current leakages for example)should flow from the power source 400 to the power conductors 246+,246−. However, if an external load 418, such as a person, is contactingthe power conductors 246+, 246−, this load 418 will present a load tothe power source 400 that will cause current I₂ to flow from the powersource 400 over the power conductors 246+, 246−. Any measured current I₂by the current measurement circuit 402 is communicated to the controllercircuit 404. In response to detection of the external load 418 as afunction of the measured current I₂ exceeding a predefined thresholdcurrent level, the controller circuit 402 is configured to communicatethe distribution power connection control signal 406 indicating adistribution power disconnect state to the distribution switch circuit408 to disconnect the power source 400 from the power conductors 246+,246− for safety reasons. This is because the external load 418 appliedto the power conductors 246+, 246− to cause the current I₂ to flow fromthe power source 400 may be a human contacting the power conductors246+, 246−.

Note that the management communications link 410 can be a separatecommunications link from the power conductors 246+, 246− or a modulatedsignal coupled to the power conductors 246+, 246− such that the remotepower connection signal 412 is modulated with power over the powerconductors 246+, 246−. If the management communications link 410 isprovided as a separate communications link, the managementcommunications link 410 may be electrical conducting wire, such ascopper wires for example. The management communications link 410 couldalso carry power to the switch control circuit 414 to power the switchcontrol circuit 414 since the management communications link 410 iscoupled to the switch control circuit 414. For example, the predefinedcurrent threshold level may be based on the voltage of the power source400 and an estimated 2,000 Ohms resistance of a human. For example, theInternational Electric Code (IEC) 60950-21 entitled “Remote PoweringRegulatory Requirements” provides that for a 400 VDC maximumline-to-line voltage, the human body resistance from hand to hand isassumed to be 2,000 Ohms resulting in a body current of 200 mA. Theremote unit 218 is eventually recoupled to the power source 400 to onceagain be operational.

After the controller circuit 404 communicates the distribution powerconnection control signal 406 indicating the distribution powerdisconnect state to the distribution switch circuit 408 to disconnectthe power source 400 from the power conductors 246+, 246−, thecontroller circuit 404 can be configured to wait a period of time and/oruntil a manual reset instruction is received before recoupling the powersource 400 to the remote unit 218. In this regard, the controllercircuit 404 can communicate the distribution power connection controlsignal 406 indicating a distribution power connect state to thedistribution switch circuit 408 to cause the distribution switch circuit408 to be closed to couple the power source 400 to the power conductors246+, 246−. The controller circuit 404 can also send the remote powerconnection signal 412 indicating a remote power connect state to theswitch control circuit 414 to generate the remote power connectionsignal 411 to cause the remote switch circuit 416 in the remote unit 218to be closed to once again couple the remote unit 218 to the powerconductor 246+ thereby connecting the load of the remote unit 218 to thepower distribution circuit 244. The capacitor C₁ in the remote unit 218is charged by the power source 400 when the remote unit 218 is coupledto the power conductors 246+, 246−. The energy stored in the capacitorC₁ allows the remote unit 218 to continue to be powered during a testingphase when the remote switch circuit 416 is open. The period of time inwhich the remote switch circuit 416 is open is such that the dischargeof the energy stored in the capacitor C₁ is sufficient to power theremote unit 218. A resistor R₁ is coupled across the remote switchcircuit 416 to allow multiple drops/remote units 218 to be connected tothe same power input 409. The overall equal parallel resistances can bea higher than the body/touch resistance of approximately 2 kOhms. Theresistance R₁ can be increased by reducing capacitance C₁ to allow afaster charging time. Powering the switch control circuit 414 in theremote unit 218 from the management communications link 410 could avoidthe need or desire to include resistor R₁ as the switch control circuit414 would be capable of powering on faster and thus also synchronizingto the power distribution circuit 244(1) faster. With continuingreference to FIG. 4, note that an optional current limiter circuit 420can be provided in the remote unit 218 and coupled to the remote switchcircuit 416. The current limiter circuit 420 is configured to limit andavoid an in-rush current, which may be identified by the powerdistribution circuit 244 as an overload. This can cause the controllercircuit 404 in the power distribution circuit 244 to send a remote powerconnection signal 411 indicating the remote power disconnect state to aremote switch input 413 to open a remote switch circuit 416 in theremote unit 218 to decouple the remote unit 218 from power conductor246+, thereby disconnecting the load of the remote unit 218 from thepower distribution circuit 244. A DC/DC converter 421 in the remote unit218 can convert a high voltage from the power source 400 (e.g., 400 V)to the required operation voltage of the load 401 (e.g. 48 V). A powerline 423 can be provided on the output side of the DC/DC converter 421to provide an operational voltage to the switch control circuit 414 foroperation. An optional load switch circuit 425 can also be providedbetween the current limiter circuit 420 and the load 401 to connect anddisconnect the load 401 from the power conductors 246+. For example, theload switch circuit 425 may be under control of the switch controlcircuit 414.

In an alternative embodiment, the load switch circuit 425 can be locallycontrolled by the switch control circuit 414 by a pulse width modulated(PWM) signal for example instead of being controlled by the remote powerconnection signal 412. The PWM rate is set by the switch control circuit414 to 0% initially. To switch control circuit 414 can graduallyincrease the PWM rate from 0% to 100% to control inrush current. Thiscan also allow the current limiter circuit 420 to be eliminated, ifdesired, but elimination or presence is not required.

In this example in FIG. 4, a fast distribution power connection controlsignal 406 is employed that is implemented at a lower protocol level forthe efficiency of the power transfer, as it allows shorter loaddisconnect time, as the power transfer is done during the loadconnecting time. A management signal that is implemented at higherprotocol level is subjected to a relatively high delay variations. In onexample, the power connection control signal 406 is implemented in thephysical level only in order to optimize it to the minimum possibledelay variation or jitter. An improved timing synchronization, betweenthe controller circuit 404 and the load disconnect control may allow ashorter load disconnecting time needed for the controller circuit 404 tocheck for lower current detection. In case of high delay variation, thedisconnect time should be larger in order to ensure additional margin inorder to allow current measurement to be conducted when there is higherconfidence that the load 401 is disconnected. FIG. 5 is a timing diagram500 illustrating an exemplary timing sequence 502 of the controllercircuit 404 in the power distribution circuit 244 in the DCS 200 in FIG.4 causing the power source 400 to be coupled to the remote unit 218 fornormal operation, and causing the power source 400 to be decoupled fromthe remote unit 218 in a testing operation to detect the external load418 in contact with the power conductors 246+, 246−. As shown in FIG. 5,the remote power connect state and remote power disconnect state of theremote switch circuit 416 as controlled by the controller circuit 404 isshown as “CLOSE” states starting at time T₀, T₂, T₄, T₆, etc. in normaloperation phases and “OPEN” states starting at time T₁, T₃, T₅, T₇, etc.in testing phases. The period of time between times T₁-T₂, T₃-T₄, andT₅-T₆ when the remote switch circuit 416 is open is controlled such thatenergy stored in the capacitor C₁ when the remote switch circuit 416 isclosed is sufficient to power the remote unit 218 during the testingphases. The current measurement circuit 402 measures the current I₂flowing through the power conductors 246+, 246− in FIG. 4. To avoidleakage, in one example, the capacitor C₁ can be charged with a lowcurrent when the remote switch circuit 416 is open, meaning off. Oncecapacitor C₁ is charged to a high enough voltage such that the switchcontrol circuit 414 can identify the remote power connection signal 412,and the remote switch circuit 416 can be turned on and off periodicallyas discussed above.

Between times T₁-T₂, T₃-T₄, and T₅-T₆, when the remote switch circuit416 is open decoupling the remote unit 218 from the power conductors246+, 246−, the controller circuit 404 detects no current flowing as anindication that the external load 418 is not contacting the powerconductors 246+, 246−. However, as shown in FIG. 5, after time T₇, thecurrent measurement circuit 402 measures a current I₂ which is detectedby the controller circuit 404, which is indicative of the external load418 being in contact with the power conductors 246+, 246−. If thecontroller circuit 404 detects the current I₂ exceeding the predefinedthreshold current level, this indicates the external load 418 being incontact with the power conductors 246+, 246−. The controller circuit 404detects the current I₂ exceeding the predefined threshold current levelshown at 504 in FIG. 5 within the detection time 506. In response, asshown in FIG. 5, the controller circuit 404 will communicate thedistribution power connection control signal 406 indicating adistribution power disconnect state to the distribution switch circuit408 to cause the distribution switch circuit 408 to be opened todecouple the power source 400 from the power conductors 246+, 246− forsafety reasons.

Turning back to FIG. 4, the power distribution circuit 244 includes apositive distribution power input 422I(P) configured to receive currentdistributed by the power source 400. A negative distribution power input422I(N) provides a return path for the current. The power distributioncircuit 244 also includes a distribution power output 422O configured todistribute the received current over the power conductor 246+ coupled tothe remote unit 218. The remote unit 218 coupled to the powerdistribution circuit 244 is deemed assigned to the power distributioncircuit 244. The distribution switch circuit 408 is coupled between thepositive distribution power input 422I(P) and the distribution poweroutput 422O. The distribution switch circuit 408 includes a distributionswitch control input 424I configured to receive the distribution powerconnection control signal 406 indicating the distribution powerconnection mode, which is either a distribution power connect state or adistribution power disconnect state. For example, the distribution powerconnection mode may be indicated by a bit in the distribution powerconnection control signal 406, where a ‘1’ bit is a distribution powerconnect state and a ‘0’ bit is a distribution power disconnect state, orvice versa. The distribution switch circuit 408 is configured to beclosed to couple the positive distribution power input 422I(P) to thedistribution power output 422O in response to the distribution powerconnection mode of the distribution power connection control signal 406indicating the distribution power connect state. The distribution switchcircuit 408 is further configured to be opened to decouple the positivedistribution power input 422I(P) from the distribution power output 422Oin response to the distribution power connection mode of thedistribution power connection control signal 406 indicating thedistribution power disconnect state.

With continuing reference to FIG. 4, the current measurement circuit 402of the power distribution circuit 244 is coupled to the distributionpower output 422O. The current measurement circuit 402 includes acurrent measurement output 426O. The current measurement circuit 402 isconfigured to measure a current at (i.e., flowing to) the distributionpower output 422O and generate a current measurement 428 on the currentmeasurement output 426O based on the measured current at thedistribution power output 422O. The power distribution circuit 244 alsoincludes a distribution management communications output 432O coupled tothe management communications link 410, which is coupled to the assignedremote unit 218. The controller circuit 404 includes a currentmeasurement input 434I communicatively coupled to current measurementoutput 426O of the current measurement circuit 402.

In an alternative embodiment, with reference to FIG. 4, the need toprovide the management communications link 410 between the controllercircuit 404 in the power distribution circuit 244 and the remote unit218 to send the remote power connection signal 412 indicating a remotepower disconnect state to a switch control circuit 414 in the remoteunit 218 can be avoided if desired. For example, the remote unit 218could be configured to cause the switch control circuit 414 (or theswitch control circuit 414 itself could be configured to) periodicallyopen the remote switch circuit 416 to decouple the remote unit 218 frompower conductor 246+ thereby disconnecting the load of the remote unit218 from the power distribution circuit 244. The remote unit 218 and/orthe switch control circuit 414 can synchronize to the controller circuit404 generating the distribution power connection control signal 406 tothe distribution switch circuit 408 to disconnect the power source 400from the power conductors 246+, 246−. For example, the switch controlcircuit 414 in the remote unit 218 can be configured to monitor changesin current I₁ on the power conductor 246+. The current I₁ will drop eachtime the distribution switch circuit 408 disconnects the power source400 from the power conductors 246+, 246−, thereby disconnecting the loadof the remote unit 218 from the power distribution circuit 244. Forexample, the controller circuit 404 can be configured to disconnect theremote unit 218 every 2 ms. The remote switch circuit 416 cansynchronize to this periodic disconnection event in a short period oftime. Thus, if the switch control circuit 414 does not see a currentdrop on power conductors 246+ within a predefined period of time whenexpected according to the expected periodic disconnect time according tothe timing determined by synchronization process, the switch controlcircuit 414 can open the remote switch circuit 416 to decouple theremote unit 218 from power conductor 246+ thereby disconnecting the loadof the remote unit 218 from the power distribution circuit 244. Theswitch control circuit 414 can close the remote switch circuit 416 torecouple the remote unit 218 to the power conductor 246+ therebyconnecting the load of the remote unit 218 from the power distributioncircuit 244 based on the expected timing of when the power distributioncircuit 244 will close the distribution switch circuit 408 according tothe timing determined by synchronization process. The discussion offurther operation of the power distribution circuit 244 and the remoteunit 218 discussed above for measuring current on the power conductors246+, 246− is also applicable for this embodiment.

In a second alternative embodiment, to avoid the need to provide aseparate management communications link 410 between the controllercircuit 404 in the power distribution circuit 244, the controllercircuit 404 could be configured to periodically drop the output voltageon the power conductor 246+ to a known voltage level (e.g., from 350 VDCto 300 VDC) before communicating the distribution power connectioncontrol signal 406 indicating a distribution power disconnect state tothe distribution switch circuit 408 to cause the distribution switchcircuit 408 to be opened to decouple the power source 400 from the powerconductors 246+, 246−. The remote unit 218 and/or the switch controlcircuit 414 therein can be configured to monitor the voltage on thepower conductor 246+ to identify this voltage drop as a remote powerconnection signal 412 indicating a remote power disconnect state. Inresponse, the switch control circuit 414 can open the remote switchcircuit 416 to decouple the remote unit 218 from the power conductor246+ thereby disconnecting the load 401 of the remote unit 218 from thepower distribution circuit 244. The remote unit 218 and/or the switchcontrol circuit 414 can wait a predefined period of time to close theremote switch circuit 416 to recouple the remote unit 218 to the powerconductor 246+ thereby connecting the load 401 of the remote unit 218from the power distribution circuit 244 based on the expected timing ofwhen the power distribution circuit 244 will close the distributionswitch circuit 408 according to the timing determined by synchronizationprocess. The discussion of further operation of the power distributioncircuit 244 and the remote unit 218 discussed above for measuringcurrent on the power conductors 246+, 246− is also applicable for thisembodiment.

In a third alternative embodiment, the management communications link410 between the controller circuit 404 in the power distribution circuit244, the controller circuit 404 could be configured to periodically dropthe output voltage on the power conductor 246+ to a known voltage level(e.g., from 350 VDC to 300 VDC) before communicating the distributionpower connection control signal 406 indicating a distribution powerdisconnect state to the distribution switch circuit 408 to cause thedistribution switch circuit 408 to be opened to decouple the powersource 400 from the power conductors 246+, 246−. The remote unit 218and/or the switch control circuit 414 therein can be configured tomonitor the voltage on the power conductor 246+ to identify this voltagedrop as a remote power connection signal 412 indicating a remote powerdisconnect state. In response, the switch control circuit 414 can openthe remote switch circuit 416 to decouple the remote unit 218 from thepower conductor 246+ thereby disconnecting the load 401 of the remoteunit 218 from the power distribution circuit 244. The remote unit 218and/or the switch control circuit 414 can wait a predefined period oftime to close the remote switch circuit 416 to recouple the remote unit218 to the power conductor 246+ thereby connecting the load 401 of theremote unit 218 from the power distribution circuit 244 based on theexpected timing of when the power distribution circuit 244 will closethe distribution switch circuit 408 according to the timing determinedby synchronization process. The discussion of further operation of thepower distribution circuit 244 and the remote unit 218 discussed abovefor measuring current on the power conductors 246+, 246− is alsoapplicable for this embodiment.

As shown in the exemplary process 600 in FIG. 6 referencing the DCS 200in FIG. 4, in one example option, the controller circuit 404 isconfigured to communicate the remote power connection signal 412comprising a remote power connection mode indicating a remote powerdisconnect state over the distribution management communications output432O coupled to the assigned remote unit 218 to cause the remote switchcircuit 416 to open and decouple the remote unit 218 from the powerconductor 246+ carrying the current I₁ (block 602 in FIG. 6). Thecontroller circuit 404 is also configured to measure a current I₂received from the power source 400 coupled to the power conductor 246+(block 604 in FIG. 6). The controller circuit 404 is configured todetermine if the measured current I₂ on the current measurement input434I exceeds a predefined threshold current level (block 606 in FIG. 6).In response to the measured current I₂ exceeding the predefinedthreshold current level indicating that the external load 418 iscontacting the power conductor 246+ or 246−, the controller circuit 404is configured to communicate the distribution power connection controlsignal 406 comprising the distribution power connection mode indicatingthe distribution power disconnect state to the distribution switchcontrol input 424I to cause the distribution switch circuit 408 to opento decouple the power source 400 from the current measurement circuit402 and the power conductor 246+ (block 608 in FIG. 6). For example, thepredefined threshold current level may be less than or equal to 200 mAor less than or equal to 100 mA, as examples. If instead, the measuredcurrent I₂ of the power distribution circuit 244 does not exceed thepredefined threshold current level, the controller circuit 404 isconfigured to communicate the distribution power connection controlsignal 406 to provide the distribution power connection mode indicatingthe distribution power connect state to the distribution switch controlinput 424I. This causes the distribution switch circuit 408 to close orcontinue to be closed and couple or continue to couple the power source400 to the current measurement circuit 402 and the power conductor 246+for providing power to the remote unit 218.

With continuing reference to FIG. 4, the controller circuit 404 is alsoconfigured to communicate the remote power connection signal 412comprising the remote power connection mode indicating the remote powerdisconnect state over the distribution management communications output432O before determining if the measured current I₂ on the currentmeasurement input 434I exceeds a predefined threshold current level.This causes the remote switch circuit 416 to open to decouple the remoteunit 218 from the power conductors 246+ or 246−. This is so that when itis desired to test to determine if the external load 418 is contactingthe power conductors 246+ or 246−, the remote unit 218 is decoupled fromthe power conductors 246+ or 246− so that the load 401 of the remoteunit 218 is not causing a current to be drawn from the power source 400.In this manner, any measured current I₂ on the current measurement input434I is an indication of the external load 418 contacting the powerconductors 246+ or 246− and not the load 401 of the remote unit 218. Aspreviously discussed, the energy stored in the capacitor C₁ when theremote unit 218 is coupled to the power conductors 246+ or 246− allowsthe remote unit 218 to continue to be powered during the testing phasewhen the remote switch circuit 416 is open.

With continuing reference to FIG. 4, after the testing phase, thecontroller circuit 404 after a predefined period of time is configuredto communicate the remote power connection signal 412 with a remotepower connection mode indicating a remote power connect state over thedistribution management communications output 432O and over themanagement communications link 410. This causes the remote switchcircuit 416 to close so that the remote unit 218 is again coupled to thepower conductor 246+ to receive power from the power distributioncircuit 244. The controller circuit 404 may be configured to communicatethe remote power connection signal 412 with a remote power connectionmode indicating a remote power connect state over the distributionmanagement communications output 432O after a predefined period of timehas elapsed communicating the remote power connection signal 412 with aremote power connection mode indicating a remote power disconnect state.The controller circuit 404 may be configured to initially communicatethe remote power connection signal 412 of the remote power connectionmode indicating the remote power connect state before communicating theremote power connection signal 412 of the remote power connection modeindicating the remote power disconnect state, so that the remote unit218 is initially powered by the power distribution circuit 244 beforeany testing phases begin. As previously discussed in reference to FIG.5, the controller circuit 404 may be configured to repeatedlycommunicate the remote power connection signal 412 of the remote powerconnection mode indicating the remote power connect state during anormal operation phase, and then communicate the remote power connectionsignal 412 of the remote power connection mode indicating the remotepower disconnect state during a testing phase to continuously detect theexternal load 418 contacting the power conductors 246+, 246−.

FIG. 7 is a graph 700 illustrating exemplary safe and unsafe regions ofbody current for a given current impulse time. The graph 700 plots abody current in mA on the X-axis, and a time impulse exposure durationin ms on the Y-axis. The curve Di illustrates a dividing line between asafe region 702 and a danger region 704 for human contact to a current.The shorter the time impulse duration of the current, the safer a humancan withstand a larger body current. For example, according to IEC60947-1, a current of 200 mA that flows through a human body for lessthan 10 ms is regarded to be safe and thus plotted in the safe region702. Therefore, in one example, power distribution circuit 244 in FIG. 4is designed in such a way that the close period of the distributionswitch circuit 408 plus the detection time 506 of current measurementcircuit 402 (see FIG. 5) will be lower than 10 ms, assuming that thetime between current detection and the disconnection of the power supply400 from the power conductors 246+, 246− by distribution switch circuit408 is negligible. This is because the current measurement circuit 402measured the current from the connected power source 400 to detect theexternal load 418, as opposed to detecting the external load 418 throughindirect methods, such as through the discharge of stored energy incapacitor C₁ that is charged when a power source is connected anddischarges during a testing phase when the power source is disconnected.In the power distribution circuit 244 in FIG. 4, the power source 400 isnot decoupled from the power conductors 246+, 246− during the testingphase when the current measuring circuit 402 is measuring current I₂. Asanother example, the power distribution circuit 244 may be configured todetect a body in contact with the power conductors 246+, 246− and causethe distribution switch circuit 408 to be opened in response withinapproximately 10 ms or less at a 200 mA body current or less as shown inarea 706 in graph 700. The power distribution circuit 244 may be alsoconfigured to detect a body in contact with the power conductors 246+,246− within approximately 20 ms or less at a 100 mA body current or lessas shown in area 708 in graph 700.

FIG. 8 is a schematic diagram illustrating the power distribution system250 in the exemplary form of the DCS 200 with the power distributioncircuit 244 configured to distribute power to a plurality of remoteunits 218(1)-218(X). Common components between the DCS 200 and the powerdistribution system 250 in FIG. 4 and FIG. 8 are shown with commonelement numbers and will not be re-described. As shown in FIG. 8, aplurality of remote units 218(1)-218(X) are provided. Each remote unit218(1)-218(X) includes a remote power input 409(1)-409(X) coupled to thepower conductors 246+(1), 246−(1), 246+(X), 246−(X), respectively, whichare configured to be coupled to the power source 400 as previouslydescribed in FIG. 4. The power distribution circuit 244 includes aplurality of power outputs 800O(1)-800O(X) each configured to providepower to a respective distribution switch circuit 408(1)-408(X) andcurrent measurement circuit 402(1)-402(X), which are assigned todifferent remote units 218(1)-218(X). The current measurement circuits402(1)-402(X) are each coupled to a respective distribution power output403(1)-403(X) coupled to respective power conductors 246+(1), 246−(1),246+(X), 246−(X). Thus, the power distribution from the powerdistribution circuit 244 to the remote units 218(1)-218(X) is in apoint-to-multipoint configuration in this example. The power conductors246+(1), 246−(1), 246+(X), 246−(X) are also coupled to remote powerinputs 409(1)-409(X). The remote units 218(1)-218(X) may also haveremote power outputs 802(1)-802(X) that are configured to carry powerfrom the respective power conductors 246+(1), 246−(1), 246+(X), 246−(X)received on the remote power inputs 409(1)-409(X) to an extended remoteunit, such as extended remote unit 218E.

Also, as shown in the DCS 200 in FIG. 8, the management communicationslinks 410(1)-410(X) to each of the remote units 218(1)-218(X) areprovided by the respective power conductors 246+ (1), 246−(1), 246+(X),246−(X). In this example, a plurality of controller circuits404(1)-404(X) are provided and dedicated to each distribution poweroutput 403(1)-403(X) to control power distribution for each pair ofpower conductors 246+(1), 246−(1)-246+(X), 246−(X) through thedistribution power outputs 403(1)-403(X) to the remote units218(1)-218(X). As will be discussed in more detail below, also in thisexample, a central management circuit 804 is provided that is configuredto send multiplexed communications to each of the remote units218(1)-218(X) to send the remote power connection signal 412 indicatinga remote power disconnect state over a respective managementcommunications link 410(1)-410(X) to decouple the respective remote unit218(1)-218(X) to from the respective power conductor 246+(1)-246+(X)thereby disconnecting the load of the remote unit 218(1)-218(X) from thepower distribution circuit 244 similar to previously described withregard to FIG. 4. Any measured current I₂ by the respective measurementcircuit 402(1)-402(X) is communicated to the respective controllercircuit 404(1)-404(X), which is in turn communicated to the centralmanagement circuit 804. In response to detection of the external load418 as a function of the measured current I₂ exceeding a predefinedthreshold current level, the central management circuit 804 isconfigured to communicate the distribution power connection controlsignal 406(1)-406(X) indicating a distribution power disconnect state tothe respective distribution switch circuit 408(1)-408(X) to disconnectthe power source 400 from the respective power conductors246+(1)-246+(X), 246−(1), 246−(X) for safety reasons. Also, as shown inFIG. 8, an extended remote unit 218E may be coupled to the remote unit218(1) and also configured to receive power from the power distributioncircuit 244 via the remote unit 218(1).

FIG. 9 is a schematic diagram illustrating an exemplary powerdistribution circuit 244 that can be employed as the DCS 200 in FIG. 8.As shown in FIG. 9, a separate positive side controller circuit 404P anda negative side controller circuit 404N are provided. This may provide alower cost solution than providing a single controller circuit 404 likein FIG. 4 to control power distribution to both the power conductors246+, 246−. The positive side controller circuit 404P controls the powerdistribution of power from the power source 400 provided to the positivedistribution power input 422I(P) to the power conductor 246 ⁻. Thenegative side controller circuit 404N controls power from the powersource 400 provided to the negative distribution power input 422I(N) tothe power conductor 246+. The previous discussion regarding the featuresand options of the controller circuit 404 above are applicable to thepositive controller circuit 404P and the negative controller circuit404N.

With continuing reference to FIG. 9, the negative controller circuit404N is configured to receive first and second current measurements428N(A), 428N(B) from first and second current measurement circuits402N(A), 402N(B). The negative controller circuit 404N is configured tocommunicate distribution power connection control signals 406N(A),406N(B) to first and second distribution switch circuits 408N(A),408N(B) to control the coupling and decoupling of the power source 400to the power conductor 246− as previously described. The reason forproviding the first and second current measurement circuits 402N(A),402N(B) and the first and second distribution switch circuits 408N(A),408N(B) is for redundancy in the event that one of the first and secondcurrent measurement circuits 402N(A), 402N(B) and/or one of the firstand second distribution switch circuits 408N(A), 408N(B) fail.

Similarly, the positive controller circuit 404P is configured to receivefirst and second current measurements 428P(A), 428P(B) from first andsecond current measurement circuits 402P(A), 402P(B). The positivecontroller circuit 404S is also configured to communicate distributionpower connection control signals 406P(A), 406P(B) to first and seconddistribution switch circuits 408P(A), 408P(B) to control the couplingand decoupling of the power source 400 to the power conductor 246+ aspreviously described. The reason for providing the first and secondcurrent measurement circuits 402P(A), 402P(B) and the first and seconddistribution switch circuits 408P(A), 408P(B) is for redundancy in theevent that one of the first and second current measurement circuits402P(A), 402P(B) and/or one of the first and second distribution switchcircuits 408P(A), 408P(B) fail. The power distribution system 250 mayservice multiple remote units 218(1)-218(X) as illustrated in the DSC200 in FIG. 8. A multiplexer circuit 900, which may also be a combinercircuit, may also be provided as shown in FIG. 9 to multiplex or combineproviding remote power connection signals 412 over the power conductors246+, 246−, as previously described.

With continuing reference to FIG. 9, isolation control lines 902A, 902Bare provided between the positive controller circuit 404P and thenegative controller circuit 404N. The isolated control line 902A is usedto communicate an immediate alarm signal 904A to both the positivecontroller circuit 404P and the negative controller circuit 404N whenthere is a need to transfer an immediate alarm signal 904A to disconnectboth the power conductor 246+, 246− due to fault detection, such as anunwanted overload alarm. Another isolation control line 902B is providedbetween the positive controller circuit 404P and the negative controllercircuit 404N. The isolated control line 902B is used as a managementlink to carry a management signal 904B from the central unit 206 tosupport management functionalities like setting new current thresholddetection levels for example. Examples of current detection thresholdscan include leakage or unwanted load detection and maximumload/overcurrent detection. Another example of management functionalityis to command the power conductors 246+, 246− to be disconnected toprevent a specific load or user from receiving power.

FIG. 10 is a schematic diagram illustrating additional exemplary detailof additional safety measures that can be provided for the powerdistribution circuit 244 of the power distribution system 250 in FIG. 8.In this example, the controller circuit 404 is configured toperiodically generate a watchdog signal 1000. For example, thecontroller circuit 404 may generate a watchdog signal 1000 every 1 ms. Awatchdog controller 1002 is provided that is configured to receive thewatchdog signal 1000 and provide a watchdog output signal 1004 inresponse. The watchdog output signal 1004 is provided to a logic circuit1006 that is configured to control the distribution power connectioncontrol signal 406. The logic circuit 1006 is designed so that if thewatchdog controller 1002 does not receive the watchdog signal 1000within a specified period of time, this means that the controllercircuit 404 may have failed or otherwise may not be operating property.In response, the watchdog output signal 1004 will be generated to causethe logic circuit 1006 to provide distribution power connection controlsignal 406 in a distribution power disconnect state to cause thedistribution switch circuit 408 to open and decouple the power supply400 from the power distribution circuit 244.

With continuing reference to FIG. 10, if a fault is detected (e.g., anunwanted overload) such that the power should be decoupled form thepower conductors 246+, 246−, the distribution power connection controlsignal 406 indicating the distribution power connection mode indicatinga power disconnection state is also provided to a status LED 1008. Anopto-coupler circuit 1010 is provided that is configured to detect thepower disconnection state from the status LED 1008 and generate theisolation control signal 904 to the positive controller circuit 404P andthe negative controller circuit 404N. This causes disconnection of powerto both the power conductor 246+, 246− due to this fault detection.

FIG. 11 is a schematic diagram illustrating another exemplary,alternative power distribution circuit 244(1) that is provided in powerdistribution system 250(1) in the exemplary form of a DCS 200(1) similarto the DCS 200 in FIGS. 2-3B. The power distribution circuit 244(1)includes the power source 400 that is configured to supply power (i.e.,current I₁) to be distributed over the power conductors 246+, 246− to aload 401 of the remote unit 218 to provide power to the remote unit 218for operation of its consuming components like the power distributioncircuit 244 in FIG. 4. Common components between the DCS 200 in FIG. 4and the DCS 200(1) in FIG. 11 are shown with common element numberstherein, and thus will not be re-described. Components shown in the DCS200(1) in FIG. 11 shown with a label of ‘(N)’ operate like theircounterpart element numbers without label of ‘(N)’ in the DCS 200 inFIG. 4.

In the DCS 200(1) in FIG. 11, the power source 400 is configured toprovide a differential voltage, in the form of a positive voltage onpower conductor 246+, a negative voltage on power conductor 246−, with aground conductor 246G. In this example, this allows an external load418(1) connected between power conductors 246+, 246−, an external load418(2) connected between power conductors 246+, 246G, an external load418(3) connected between power conductors 246−, 246G to be detected bythe power distribution circuit 244(1). To detect an external load 418(3)connected between power conductors 246−, 246G, another second currentmeasurement circuit 402(N) is provided and coupled to the powerconductor 246−. When non-zero current I₃ is measured by currentmeasurement circuit 402(N), when remote switch circuit 416 is open, thecontroller circuit 404 uses this as an indication that an external load418(3) is connected between power conductors 426- and 426G and directsthe distribution switch circuit 408(N) to be opened.

The controller circuit 404 may also be configured to compare thecurrents I₂, I₃ measured by current measurement circuits 402, 402(N). Ifthe currents I₂, I₃ are not substantially identical, the controllercircuit 404 may conclude that current flows through an external loadcontacting between either power conductors 246+, 246− to the groundpower conductor ground 426G. In this instance, the controller circuit404 may cause distribution switch circuits 408 and 408(N) to both beopened to decouple the power source 400 from power conductors 246+,246−.

Also as shown in FIG. 11, a distribution multiplexer circuit 1100 isprovided in the power distribution system 250(1). A remote multiplexercircuit 1102 is provided in the remote unit 218. For example, similar topreviously discussed in FIG. 8, the distribution multiplexer circuit1100 may allow a single controller circuit 404 (or central managementcircuit therein as provided in FIG. 8), to communicate the distributionpower connection control signal 406 to a plurality of remote units 218one at a time. The distribution multiplexer circuit 1100 multiplexes theremote unit 218, the distribution power connection control signal 406 issent. The multiplexing may be based on frequency-domain multiplexing(FDM) or time-domain multiplexing (TDM) as non-limiting examples. Theremote multiplexer circuit 1102 can demultiplex the distribution powerconnection control signal 406 for instruction.

It may also be desired for example, to include a diode bridge circuit1104 (e.g., a full bridge diode circuit) coupled to the power input 409in the remote unit 218 (e.g., can be part of the remote multiplexercircuit 1102) to in case the power distribution circuit 244(1)identifies fault/or unwanted load, and the controller circuit 404disconnects distribution switch circuits 408. The diode bridge circuit1104 can block any potential stored energy from discharging towards thepower conductors 246+, 246−. Adding a diode bridge circuit 1104 can alsomake the power input 409 of the remote unit 218 indifferent (i.e.,insensitive) to the polarity of the power conductors 246+, 246− suchthat the remote unit 218 can function even if there is a polarityreversal in the power conductors 246+, 246−. However a drawback may bethat for high current transfer, there is a relatively high power loss inthe diode bridge circuit 1104 (e.g., 5 A on 2 V requires 10 W of heatdissipation).

Note that any of the referenced inputs herein can be provided as inputports or circuits, any of the referenced outputs herein can be providedas output ports or circuits.

FIG. 12 is a schematic diagram representation of additional detailillustrating a computer system 1200 that could be employed in anycomponent in the DCS 200, including but not limited to the controllercircuits 404 in the power distribution systems 250, 250(1) for couplinga remote unit 218 to the power source 400 during a normal operationphase and instructing the remote unit 218 to decouple from the powersource 400 during testing phases to then measure current from the powersource 400 during a testing phase, including but not limited to the DCS200 in FIGS. 4, 8 and 11 and the controller circuits 404, 404M, 404S inFIGS. 4 and 8-11. In this regard, the computer system 1200 is adapted toexecute instructions from an exemplary computer-readable medium toperform these and/or any of the functions or processing describedherein.

In this regard, the computer system 1200 in FIG. 12 may include a set ofinstructions that may be executed to program and configure programmabledigital signal processing circuits in a DCS for supporting scaling ofsupported communications services. The computer system 1200 may beconnected (e.g., networked) to other machines in a LAN, an intranet, anextranet, or the Internet. While only a single device is illustrated,the term “device” shall also be taken to include any collection ofdevices that individually or jointly execute a set (or multiple sets) ofinstructions to perform any one or more of the methodologies discussedherein. The computer system 1200 may be a circuit or circuits includedin an electronic board card, such as, a printed circuit board (PCB), aserver, a personal computer, a desktop computer, a laptop computer, apersonal digital assistant (PDA), a computing pad, a mobile device, orany other device, and may represent, for example, a server or a user'scomputer.

The exemplary computer system 1200 in this embodiment includes aprocessing device or processor 1202, a main memory 1204 (e.g., read-onlymemory (ROM), flash memory, dynamic random access memory (DRAM), such assynchronous DRAM (SDRAM), etc.), and a static memory 1206 (e.g., flashmemory, static random access memory (SRAM), etc.), which may communicatewith each other via a data bus 1208. Alternatively, the processor 1202may be connected to the main memory 1204 and/or static memory 1206directly or via some other connectivity means. The processor 1202 may bea controller, and the main memory 1204 or static memory 1206 may be anytype of memory.

The processor 1202 represents one or more general-purpose processingdevices, such as a microprocessor, central processing unit, or the like.More particularly, the processor 1202 may be a complex instruction setcomputing (CISC) microprocessor, a reduced instruction set computing(RISC) microprocessor, a very long instruction word (VLIW)microprocessor, a processor implementing other instruction sets, orother processors implementing a combination of instruction sets. Theprocessor 1202 is configured to execute processing logic in instructionsfor performing the operations and steps discussed herein.

The computer system 1200 may further include a network interface device1210. The computer system 1200 also may or may not include an input1212, configured to receive input and selections to be communicated tothe computer system 1200 when executing instructions. The computersystem 1200 also may or may not include an output 1214, including butnot limited to a display, a video display unit (e.g., a liquid crystaldisplay (LCD) or a cathode ray tube (CRT)), an alphanumeric input device(e.g., a keyboard), and/or a cursor control device (e.g., a mouse).

The computer system 1200 may or may not include a data storage devicethat includes instructions 1216 stored in a computer-readable medium1218. The instructions 1216 may also reside, completely or at leastpartially, within the main memory 1204 and/or within the processor 1202during execution thereof by the computer system 1200, the main memory1204 and the processor 1202 also constituting computer-readable medium.The instructions 1216 may further be transmitted or received over anetwork 1220 via the network interface device 1210.

While the computer-readable medium 1218 is shown in an exemplaryembodiment to be a single medium, the term “computer-readable medium”should be taken to include a single medium or multiple media (e.g., acentralized or distributed database, and/or associated caches andservers) that store the one or more sets of instructions. The term“computer-readable medium” shall also be taken to include any mediumthat is capable of storing, encoding, or carrying a set of instructionsfor execution by the processing device and that cause the processingdevice to perform any one or more of the methodologies of theembodiments disclosed herein. The term “computer-readable medium” shallaccordingly be taken to include, but not be limited to, solid-statememories, optical medium, and magnetic medium.

The embodiments disclosed herein include various steps. The steps of theembodiments disclosed herein may be formed by hardware components or maybe embodied in machine-executable instructions, which may be used tocause a general-purpose or special-purpose processor programmed with theinstructions to perform the steps. Alternatively, the steps may beperformed by a combination of hardware and software.

The embodiments disclosed herein may be provided as a computer programproduct, or software, that may include a machine-readable medium (orcomputer-readable medium) having stored thereon instructions, which maybe used to program a computer system (or other electronic devices) toperform a process according to the embodiments disclosed herein. Amachine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes: amachine-readable storage medium (e.g., ROM, random access memory(“RAM”), a magnetic disk storage medium, an optical storage medium,flash memory devices, etc.); and the like.

Unless specifically stated otherwise and as apparent from the previousdiscussion, it is appreciated that throughout the description,discussions utilizing terms such as “processing,” “computing,”“determining,” “displaying,” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data and memories represented asphysical (electronic) quantities within the computer system's registersinto other data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission, or display devices.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various systems may beused with programs in accordance with the teachings herein, or it mayprove convenient to construct more specialized apparatuses to performthe required method steps. The required structure for a variety of thesesystems will appear from the description above. In addition, theembodiments described herein are not described with reference to anyparticular programming language. It will be appreciated that a varietyof programming languages may be used to implement the teachings of theembodiments as described herein.

Those of skill in the art will further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithms describedin connection with the embodiments disclosed herein may be implementedas electronic hardware, instructions stored in memory or in anothercomputer-readable medium and executed by a processor or other processingdevice, or combinations of both. The components of the distributedantenna systems described herein may be employed in any circuit,hardware component, integrated circuit (IC), or IC chip, as examples.Memory disclosed herein may be any type and size of memory and may beconfigured to store any type of information desired. To clearlyillustrate this interchangeability, various illustrative components,blocks, modules, circuits, and steps have been described above generallyin terms of their functionality. How such functionality is implementeddepends on the particular application, design choices, and/or designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentembodiments.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a processor, a Digital Signal Processor (DSP), anApplication Specific Integrated Circuit (ASIC), a Field ProgrammableGate Array (FPGA), or other programmable logic device, a discrete gateor transistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Furthermore,a controller may be a processor. A processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration).

The embodiments disclosed herein may be embodied in hardware and ininstructions that are stored in hardware, and may reside, for example,in RAM, flash memory, ROM, Electrically Programmable ROM (EPROM),Electrically Erasable Programmable ROM (EEPROM), registers, a hard disk,a removable disk, a CD-ROM, or any other form of computer-readablemedium known in the art. An exemplary storage medium is coupled to theprocessor such that the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium may be integral to the processor. The processor and the storagemedium may reside in an ASIC. The ASIC may reside in a remote station.In the alternative, the processor and the storage medium may reside asdiscrete components in a remote station, base station, or server.

It is also noted that the operational steps described in any of theexemplary embodiments herein are described to provide examples anddiscussion. The operations described may be performed in numerousdifferent sequences other than the illustrated sequences. Furthermore,operations described in a single operational step may actually beperformed in a number of different steps. Additionally, one or moreoperational steps discussed in the exemplary embodiments may becombined. Those of skill in the art will also understand thatinformation and signals may be represented using any of a variety oftechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips, that may be referencesthroughout the above description, may be represented by voltages,currents, electromagnetic waves, magnetic fields, or particles, opticalfields or particles, or any combination thereof.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order. Accordingly, where a method claim doesnot actually recite an order to be followed by its steps, or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is in no way intendedthat any particular order be inferred.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the invention. Since modifications, combinations,sub-combinations and variations of the disclosed embodimentsincorporating the spirit and substance of the invention may occur topersons skilled in the art, the invention should be construed to includeeverything within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. A remote antenna unit, comprising: a remote powerinput coupled to a power conductor carrying current from a powerdistribution circuit; a remote switch circuit comprising a remote switchinput configured to receive a remote power connection signal; the remoteswitch circuit configured to be closed to couple to the remote powerinput; and the remote switch circuit further configured to be opened todecouple from the remote power input; a switch control circuit coupledto the remote switch circuit and configured to periodically open theremote switch circuit to decouple from the remote power input; and atleast one antenna, wherein the remote antenna unit is configured to:distribute one or more downlink communications signals received from oneor more downlink communications links, to one or more client devices;and distribute one or more uplink communications signals from the one ormore client devices to one or more uplink communications links.
 2. Theremote antenna unit of claim 1, wherein the antenna distributes the oneor more downlink communications signals and through which the remoteantenna unit receives the one or more uplink communications signals. 3.The remote antenna unit of claim 2, further comprising a remotemanagement communications input coupled to a management communicationslink.
 4. The remote antenna unit of claim 3, wherein the switch controlcircuit comprises a remote switch control input configured to receivethe remote power connection signal over the remote managementcommunications input, wherein the remote power connection signal causesthe switch control circuit to open the remote switch circuit.
 5. Theremote antenna unit of claim 2, wherein: the one or more downlinkcommunications links comprise one or more optical downlinkcommunications links; and the one or more uplink communications linkscomprise one or more optical uplink communications links.
 6. The remoteantenna unit of claim 5, further comprising: one or moreoptical-to-electrical (O-E) converters configured to convert thereceived one or more optical downlink communications signals into one ormore electrical downlink communications signals; and one or moreelectrical-to-optical (E-O) converters configured to convert receivedone or more electrical uplink communications signals into the one ormore optical uplink communications signals.
 7. The remote antenna unitof claim 2, wherein the switch control circuit is configured to detect achange in voltage level at the remote power input from a first voltagelevel to a second voltage level.
 8. The remote antenna unit of claim 7,wherein the switch control circuit is configured to detect a change inthe voltage level at the remote power input from the second voltagelevel to the first voltage level.
 9. The remote antenna unit of claim 2,further comprising: an extended remote communications output configuredto be coupled to an extended downlink communications link coupled to anextended remote unit; and an extended remote power output configured tobe coupled to an extended power conductor to carry current from theremote antenna unit to the extended remote unit.
 10. A method ofcontrolling a remote antenna unit, the method comprising: receivingcurrent from a power distribution circuit at a remote power input;responsive to a remote power connection signal, periodically opening aremote switch circuit to decouple power consuming elements of the remoteantenna unit from the remote power input; periodically generating theremote power connection signal with a switch control circuit;distributing one or more downlink communications signals received fromone or more downlink communications links, to one or more clientdevices; distributing one or more uplink communications signals throughat least one antenna from the one or more client devices to one or moreuplink communications links; and receiving through a remote managementcommunications input, the remote power connection signal, wherein theremote power connection signal causes the switch control circuit to openthe remote switch circuit.
 11. The method of claim 10, furthercomprising detecting a change in voltage level at the remote power inputfrom a first voltage level to a second voltage level.
 12. The method ofclaim 11, further comprising detecting a change in the voltage level atthe remote power input from the second voltage level to the firstvoltage level.
 13. The method of claim 11, further comprising: couplingthe remote antenna unit to an extended downlink communications linkcoupled to an extended remote unit; and sending current from the remoteantenna unit to the extended remote unit.
 14. The method of claim 10,further comprising: coupling the remote antenna unit to an extendeddownlink communications link coupled to an extended remote unit; andsending current from the remote antenna unit to the extended remoteunit.
 15. A power distribution system comprising: a power distributioncircuit comprising: a distribution power input configured to receivecurrent distributed by a power source; a distribution power outputconfigured to distribute the received current over a power conductorcoupled to an assigned remote unit among a plurality of remote units; adistribution switch circuit coupled between the distribution power inputand the distribution power output, the distribution switch circuitcomprising a distribution switch control input configured to receive adistribution power connection control signal indicating a distributionpower connection mode; the distribution switch circuit configured to beclosed to couple the distribution power input to the distribution poweroutput in response to the distribution power connection mode indicatinga distribution power connect state; and the distribution switch circuitfurther configured to be opened to decouple the distribution power inputfrom the distribution power output in response to the distribution powerconnection mode indicating a distribution power disconnect state; and acurrent measurement circuit coupled to the distribution power output andcomprising a current measurement output; the current measurement circuitconfigured to measure a current at the distribution power output andgenerate a current measurement on the current measurement output basedon the measured current at the distribution power output; and acontroller circuit comprising: a current measurement inputcommunicatively coupled to a current measurement output of the currentmeasurement circuit of the power distribution circuit; and thecontroller circuit configured to: generate the distribution powerconnection control signal indicating the distribution power connectionmode to the distribution switch control input of the power distributioncircuit indicating the distribution power connect state; determine ifthe measured current on a current measurement input among the one ormore current measurement inputs of the power distribution circuitexceeds a predefined threshold current level when the distributionswitch circuit is closed to couple the distribution power input to thedistribution power output; in response to the measured current of thepower distribution circuit exceeding the predefined threshold currentlevel, communicate the distribution power connection control signalindicating the distribution power connection mode to the distributionswitch control input of the power distribution circuit indicating thedistribution power disconnect state; and communicate a remote powerconnection signal comprising a change in voltage levels indicating aremote power disconnect state to cause the assigned remote unit todecouple current from the power conductor of the power distributioncircuit.
 16. The power distribution system of claim 15, in response tothe measured current of the power distribution circuit not exceeding thepredefined threshold current level, communicate the distribution powerconnection control signal comprising the distribution power connectionmode to the distribution switch control input of the power distributioncircuit indicating the distribution power connect state.
 17. The powerdistribution system of claim 15, wherein the controller circuit isfurther configured to communicate the remote power connection signalcomprising a remote power connection mode indicating the remote powerdisconnect state before determining if the measured current on thecurrent measurement input exceeds the predefined threshold currentlevel.
 18. The power distribution system of claim 15, wherein thecontroller circuit is further configured to communicate the remote powerconnection signal comprising a remote power connection mode indicating aremote power connect state over a distribution management communicationsoutput coupled to the assigned remote unit to the power distributioncircuit to cause the assigned remote unit to couple to the powerconductor of the power distribution circuit.
 19. The power distributionsystem of claim 18, wherein the controller circuit is configured tocommunicate the remote power connection signal comprising the remotepower connection mode indicating the remote power connect state after apredefined time has elapsed after communicating the remote powerconnection signal comprising the remote power connection mode indicatingthe remote power disconnect state.
 20. The power distribution system ofclaim 19, wherein the remote power connection signal indicating theremote power connect state comprises a change in voltage level thatincreases the voltage level.
 21. The power distribution system of claim15, wherein the predefined threshold current level is less than 200milliAmps (mA).
 22. The power distribution system of claim 15, whereinthe predefined threshold current level is less than 100 milliAmps (mA).23. The power distribution system of claim 15, wherein the controllercircuit is further configured to periodically generate a watchdogsignal; and further comprising a watchdog controller configured to:receive the watchdog signal; and in response to not receiving thewatchdog signal within a predefined time period, cause the distributionpower connection control signal to indicate the distribution powerdisconnect state.
 24. A power distribution system comprising: a powerdistribution circuit comprising: a distribution power input configuredto receive current distributed by a power source; a distribution poweroutput configured to distribute the received current over a powerconductor coupled to an assigned remote unit among a plurality of remoteunits; a distribution switch circuit coupled between the distributionpower input and the distribution power output, the distribution switchcircuit comprising a distribution switch control input configured toreceive a distribution power connection control signal indicating adistribution power connection mode; the distribution switch circuitconfigured to be closed to couple the distribution power input to thedistribution power output in response to the distribution powerconnection mode indicating a distribution power connect state; and thedistribution switch circuit further configured to be opened to decouplethe distribution power input from the distribution power output inresponse to the distribution power connection mode indicating adistribution power disconnect state; and a current measurement circuitcoupled to the distribution power output and comprising a currentmeasurement output; the current measurement circuit configured tomeasure a current at the distribution power output and generate acurrent measurement on the current measurement output based on themeasured current at the distribution power output; and a controllercircuit comprising: a current measurement input communicatively coupledto a current measurement output of the power distribution circuit; andthe controller circuit configured to: generate the distribution powerconnection control signal indicating the distribution power connectionmode to the distribution switch control input of the power distributioncircuit indicating the distribution power connect state; determine ifthe measured current on a current measurement input among the one ormore current measurement inputs of the power distribution circuitexceeds a predefined threshold current level when the distributionswitch circuit is closed to couple the distribution power input to thedistribution power output; in response to the measured current of thepower distribution circuit exceeding the predefined threshold currentlevel, communicate the distribution power connection control signalindicating the distribution power connection mode to the distributionswitch control input of the power distribution circuit indicating thedistribution power disconnect state; lower a voltage level on thedistribution power output from a first voltage level to a second voltagelevel distributing the received current over the power conductor coupledto the assigned remote unit; and raise the voltage level on thedistribution power output from the second voltage level to the firstvoltage level distributing the received current over the power conductorcoupled to the assigned remote unit.